Grinding-wheel dressing fixture



Feb. 26, 1952 H. H. GOTBERG ET AL GRINDING-WHEEL DRESSING FIXTURE Filed June 23, 1950 5 Sheets-Sheet l Feb- 26, 1952 H. H. G01-BERG ET AL 2,586,937

GRINDING-WHEEL DRESSING FIXTURE Filed June 25, 1950 5 Sheets-Sheet 2 INVEN ORS /7/4/2'5/ /74 622x ef?,

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Feb- 26, 1952 H. H. GOTBERG ET Al. 2,586,937

GRINDING-WHEEL DRESSING FIXTURE Filed June 2s, 195oA 5 sheets-sheet 5 .96 4 22, r `f Ei.

Feb. 26, 1952 H. H. G01-BERG ETAL GRINDING-WHEEL DRESSING FIXTURE 5 Sheets-Sheet 4 Filed June 23, 1950 Feb- 26, 1952 H. H. GOTBERG ET AL 2,586,937

GRINDING-WHEEL DRESSING FIXTURE Filed June 23, 1950 5 Sheets-Sheet 5 `i i l L Ell- H aF/KEYS.

Patented Feb. 26, 1952 GRINDING-WHEEL DRESSING FIXTURE Harry H. Gotbcrg and Joseph Silvagi, Detroit, Mich., assignors to Colonial Broach Company, Warren Township, Mich., a corporation of Delaware Application June 23, 1950, Serial No. 169,888

Y 8 Claims. l

This invention relates broadly to grindingwheel dressing fixtures and more particularly to a fixture for dressing the involute side surfaces of gear grinding wheels.

Specifically, this invention is an improvement in the wheel dressing fixture disclosed in the Kopec Patent No. 2,321,825, dated June 15, 1943.

The patented fixture is adapted to grind the involute surfaces on opposite sides of a gear grinding wheel without necessity of moving the fixture when the dressing point is moved from one side of the wheel to the other. Fundamentally, the dressing device comprises a wheel dressing point carried by a parallelogram linkage, bnc pivot of which is fixed to a suitable support and another pivot of which has an extension constituting a follower for master cam members also mounted on the support. When the follower is moved along the cam surfaces the wheel dressing point of the device is caused to move in an involute pathconforming to the desired shape of the grinding wheel.

In actual practice, however, prior art devices of the type hereinabove referred to are defective in operation because the wheel-dressing point is not maintained at all times in proper relation to the surface being ground. As a consequence, the point is presented differently to different parts of the surface; and since these points are irregular in shape, inaccuracies in the ground surface of the wheel result. These inaccuracies are, in turn, transferred to the gear hground by the wheel so that a faulty or imperfect gear is produced. I

We have now discovered that the above defects in grinding-wheel dressers of the type shown in the Kcpec patent can be obviated by keeping the wheel-dressing point exactly normal or perpendicular at all times to the surface being dressed, and have devised a modied construction for achieving and maintaining this relationship. When the dressing xture is constructed according to thepresent invention, a substantially true involute surface is produced on the grinding wheel and uniform grinding of every wheel acted upon by the fixture is obtained. As a consequence, imperfect gears resulting from faulty dressing of the Wheel used to grind the gears are eliminated.

, From the foregoing it Will be readily apparent that a primary object of the present invention is to reconstruct grinding-Wheel dressing fixtures of the4 type shown in the Kopec patent supra so `as to eliminate imperfections heretofore inherent in the fixture.

Other objects and advantages of the invention will be apparent during the course of the following description. n

In the drawings forming a part of this specification and wherein like numerals are employed to designate like parts throughout the same:l

Fig. 1 is a front elevational view of a grindingwheel dressing fixture embodying the invention;

Fig. 2 is a fragmentary, vertical sectiona1 view taken on the line 2-2 of Fig. 1;

Fig. 3 is a top plan view of the fixture; I

Fig. 4 is a side-elevational view of the same;

Fig. 5 is an enlarged, fragmentary, verticalsectional view taken on the line 5 5 of Fig. l;

Fig. 6 is a rear elevational view of the fixture;

Fig. 7 is a sectional view taken on the lines '1 1 of Fig. l; l A

Fig. 8 is a vertical sectional view taken on the line 8 8 of Fig'. 4;

Fig. 9 is a fragmentary sectional view taken on the line 9-9 of Fig. 1;

Fig. 10 is a fragmentary sectiona1 view taken on the line Ill-I 0 of- Fig. 1;

Fig. 11 is a fragmentary sectiona1 view taken on the line Il-I I of Fig. 1;and

Fig. 12 is an enlarged, fragmentary sectional view taken on the line 12-12 of Fig. 4.

In the drawings, wherein for the purpose of illustration is shown a preferred embodiment of the invention, the various moving parts of the fixture are mounted on an upright support having a relatively large, horizontal base 22 porvided with the usual adjusting pads 24. Immediately ahead ofthe support 20 on the base 22 is a fiat -supporting surface 26 on which a relatively small, upright, outboard support 28 is mounted and fastened securely in place by means of-pins 30 and screws 32 (Fig. 1). v

Mounted on the front of the support 20 is a pair of master cam members 34 and 36 having master cam surfaces 38 and 40 respectively-of conventional shape for producing, in conjunction with other mechanisms hereinafter described, movement of a wheel-dressing point along a true involute curve. More particularly, the master cams 34 and 3S are juxtaposed on the support 2D with the cam surfaces 38 and 40 side by side in confrontingrelation. At the` inner bottom corners offthe cams 34 and 36 are laterally extending tabs 42 and 44 respectively of reduced thickness and in overlapping relation as perhaps bestshown in Figs. 5 and 8. A headed pivot pin extends forwardly through the supports 20 and 2B and the tabs 42 and 44 are pivoted on the pins between the supports.

It is necessary to adjust the cams 34 and 36 angularly about pivot 40; and in order to hold them in a selected angularly adjusted position, each cam carries headed bolts 50 and 52 which extend through arcuate slots 54 and 56 respectively in the support 20. Washers 58 land 80 are provided on the projecting terminal portions of bolts 50 and 52, and wing nuts 02 and 64 also on the bolts are tightened against the washer to hold the cams solidly in selected adjusted positions. The heads of screws 50 and 52 preferably are countersunk iiush with the forward surfaces of master cams 34 and 30 so that working parts hereinafter described in detail are free to move on the cams. It will be readily apparent in this connection that slots 54- and 56 are struck on arcs having the axis of pivots 40 as a center so that the cams 34 and 33 are .free to adjust about the pivots. Sine bar buttons 60 and 08 (Fig. 6) are provided at the bottom outside corners of the master cams 34 and 30 as reference surfaces for use in angular adjustment of the cams.

Also mounted on the pivot pin 45 and in front l of the master cams 34 and 3E are links 10, 72,

14, and l arranged generally in the form of a parallelogram and fastened together at the ends thereof by pivots '18, 80, and 82 disposed equidistantly apart. As perhaps best shown in Fig. l, the parallelogram linkage is disposed upright in front of the master cams 34 and 30. In the interest of compactness links and I4 are disposed in the same vertical plane, and the other two links l2 and l5 overlie links '10 and 14. The

upper pivot 80 of the linkage has a rearward r extension which denes a follower 84 for the master cams 34 and 30 and a handle 80 for manually moving the follower along the cam surfaces 38 and 40. This parallelogram linkage carries the wheel dressing point 0f the fixture and defines a pantograph which moves the dressing point in an involute path when the follower 84 is moved along one or the other of cam surfaces 38 and 40. In order to operate the linkage without interference from the supports, link l0 is mounted with the lower end thereof between the master cams 34 and 36 and the outboard support 28 (Fig. 5), and the pivoted end of the link l0 preferably is rabbeted as at 88. The lower end of link 'l2 also is mounted on the pivot 46 but forwardly of support 28, and the parts are held properly assembled by a set screw 90 which extends from one side of the link 'l2 into an annular groove 92 in pivot 40.

In order to hold the follower 84 pressed solidly y against the cam surfaces 38 and 40 at all times during operation of the xture, a pivoted supporting arm 94 is mounted on the pivot 46 behind the main support 20 and this arm has an outwardly offset terminal portion Bwhich is connected to a pivoted lug 08 on the handle 8B by a spring |00. The supporting arm 94 is movable between the full-line and broken-line positions shown in Fig. 6 and is held securely in either one of the two positions by a lock pin |02 which extends through an opening in the arm and into suitably positioned sockets in the support 20. One end of a chain |04 is here shown fastened to the pin |02 by a screw |06, and the other end of the chain is fastened to any suitable or convenient part of the support 20 (not shown) to prevent the pin from being lost or mislaid when disengaged from the arm 04. A washer |08 on the follower 84 at the outer side of the master cams 34 and 38 coiii) 4 operates with link 14 in holding the follower on the cam surfaces.

In use, the arm 04 is moved to the full-line position (Fig. 6) when it is desired to move the follower 84 along the cam '36. When the arm is thus positioned, spring |00, which normally is maintained under tension, holds the follower 84 pressed downwardly against the cam 38 at all times during movement thereof along the cam surface 40. Conversely, when it is desired to move follower 84 along cam surface 34, the arm 94 is swung to the broken-line position (Fig. 6). In this position of the arm, spring |00 is disposed to press the cam follower 84 downwardly against cam 34 at all times during movement of the follower along cam surface 38.

In order to vary the ratio of the curve described by the dressing point and the curve of the master cam, an adjustable cross link ||0 is mounted on the pantograph. Specifically, the cross link ||0 is supported on opposite links l2 and l5 and parallel to links 'l0 and 14 by mountings||2 and |14. Pivots H0 and ||8 fasten the cross link H0 on mounting blocks ||2 and H4.

In order to adjust mounting I2 longitudinally along link l2, the latter is formed with a longitudinal slot |20 in which an adjusting screw |22 is mounted. One end of the screw |22 extends from the link l2, and the projecting portion thereof is provided with a manually operable handle |24. The mounting block ||2 is formed at opposite sides thereof with anges |26 and |28 which embrace the link l2 to guide the mounting block in its travel thereon. Between flanges |20 and |28 the mounting ||2 is formed with a tongue or rib |38 which fits snugly in the slot |20 and threadedly receives the adjusting screw |22. The mounting block ||2 is held securely but slidably on the link 'I2 by a retaining plate |32 which is fastened to the distal edge of tongue by screws |34. It will be observed (Fig. 7) that retaining plate |32 extends laterally of the tongue |30 and that the projecting portions thereof travel in ways |30 and |38 to hold the block H2 on the link 'I2 while permitting the same to be freely adjustable on the link. A set screw |40 carried by and extending inwardly through flange |23 can be tightened against link l2 to hold the mounting block ||2 in a selected adjusted position on the link. In-the particular construction here shown by way of illustration, the pivot IIS is fixed to the cross link H0 and is rotatably associated with the mounting block by means of a cross pin |42 which interts with a peripheral groove |44 in the pin.

The other mounting H4 is associated with cross link ||0 and parallelogram link T6 in the same manner as mounting ||2. As shown in Fig. 1, the parallelograrn link l5 is formed with a longitudinal slot |46 and an adjusting screw |48 eX- tends longitudinally therethrough. The screw |48 extends from one end of link l5 and the projecting end of the screw is provided with a manually operable handle |50. Mounting i4 has side flanges |52 and |54 disposed in embracing relation to link l0 and a middle rib |50 which ts snugly but slidably in slot |46. Adjusting screw |48 extends thro-ugh and threadedly engages the rib so that rotation of the screw moves the mounting longitudinally along link 10. A retaining plate |53 fastened to rib |55 by screws |30 holds the mounting block securely but slidably on link l5. Also it will be observed that pivot H8 press-fitted or otherwise fixed to cross link H0 is loosely journaled in the mounting block ||4 and held .against longitudinal. move,- ment by a cross pin |62=which interfitswith a peripheral groove |64 in the pin. Aset screwl |66 carried by the ange |52 of mounting li4can be tightened against link 'I6 tohold the mounting block ||4 in a selected adjusted'position.

A chuck for the wheel dressing .point is mounted on andlongitudinally adjustable along the cross link l |0. The chuck includes a mounting block |68 which is substantially identical to mounting blocks ||2 and ||4 hereinabove described. In this connection it will be observed that cross link is-formed with a longitudinal slot and that a longitudinal adjusting 'screw |12 is provided in the slot. One end of screw |12 extends from cross links ||0 and the projecting portion thereof is providedv with a transverse manually operable handle |74. block |68 has side flanges |16 and |18 which straddle across link ||0 and .a rib |80 which nts The mounting snugly but slidably in the slot |78 yand threadedly receives adjusting screw |12. The mounting block |68 is held on cross link ||01.as..in the mountings previously described by means of a retaining plate |82 which is fastened to the rib by a screw |84. The adjusting screw .|12 is rotated to move mounting |68 along the link ||0 and a set screw |86 carried by the mounting Vis tightened against the link to hold the mounting in a selected adjusted position.

The .chuck also includes an arm |88 .having a radial flange |90 .at one end thereof which nts snugly but rotatably into a socket |92 provided in the face of mounting block |68. The arm |88 is held on the mounting block by va retainingplate |94 which ts snugly around the varm and is fastened securely to the block bya pluralityof screws |86.

Arm |88 has a laterally'oiset bifurcated'terminal portion |88 which carries .the diamond dressing point 260. The latter is conventional, having a threaded casing 202 which is vlongitudinally adjustable relative to the varm |88 by means of a thumb nut204 disposed '.betweenth terminal bifurcations of the arm.

According to the presentinvention, a block 206 is detachably fastened-to `thearm |88 .byasp'ringloaded detent 288, and adjacent corners ofthe block are connected to the distal ends .of parallelogram links 10 and 'F2 respectively by control arms 2|6 and 2|2. In the form of the invention here shown by way of illustration, the .inner adjacent ends of links 2|0 and 2.12 .extend Vinto slots 2|4 and 2li:` respectively .provided iin the upper corners of block 206 and theterminal .portions disposed within the blocks Aare fastened .by pivots 2|8 and 220. The outer distal endsofthe control arms 2|8 and 2|2 are pivotally fastened to studs 222 -and 224 respectively-.which in turn are fastened to the ends of links 18 .and 12. In this latter connection it will be observed .that studs 222 and 224 have reduced terminal portions 226 and 228 respectively which extendthrough longitudinal slot-s 238 and 232 in thecontrol arms and 2|2. Screws 284 and 236 hold the Vcontrol arms 2|@ and 2| 2 on the reduced terminal portions 226 and 228, and cross .screws 238tand 248 hold the reduced ternfinal .portions atthe outer ends of their respective slots.

In order to position the point 200.for .properly y dressing the opposite involute `surfaces o'f the grinding wheel, it is necessary to hold arm |88 in two positions 180 apart. To this end thearm |88 is provided at opposite rsidesi.thereof.V with openings 242 and 2.44which receive-thevdetent 2.08. When thedetent 208 is retracted: indisch-'-` gagearm |88, the Iattercan be positioned-either asshown in Fig. 1 or in a position 180 with respect thereto. In one position of the arm, detent 208 registers with opening 244 as perhaps .best shown in Fig. 12, and in the other position of the arm the detentregisters with opening 242.

For convenience, the block 206 preferably-is made in two parts. here designated 20Go and 2061i,` the two parts being connected at one side thereof by a hinge designated generally 246. A latch bolt.248 is fastened to part 206er by pivot 250 at the side thereof remote from hinge 246, andthe latch extends through a slot 252 in the correspondingside of part 28612. A nut 254 on the end of the latch bolt 248 is tightened toholdthetwo parts of the block together and around' arm: |88.

-Itof course is. not necessary to remove block 206 entirelyfrom the arm |88 when the latter is moved from one position to the other. To accomplish this adjustment it is merely necessary to disengage the detent 208, rotate arm |88V to the desired position, and then again engage the detent with the aligned opening 242 or 244. There are occasions, however, as when it is necessary toadapt the device for dressing a different size grinding wheel, when it is necessary or desirable to substitute a larger or smaller arm |88. On these occasions the latch bolt 248 is disengaged to release mounting section 2|liibso that the latter falls away from the arm and automatically disengages the detent 208. Screws |96are then removed to disengage'retaining plate |94and to permitcomplete removal ofv the armi |88. i

In order to dress the periphery ofthe grindingwheel, asecond dressing point '266 is provided, which pointV convenientlymay-be similar-or identicalY to the dressing point 208 hereinabove described and is carried by a suitable chuck 258. The latter, in turn, is carried by and projects horizontally from a vertical slide 260 mounted in the guideway 262 of a vertical block 264 which is supported in proper relation with respect'to the grinding wheel by a pair of arms 266 and 268; The supporting arms 266 and 268 arefastened to the upright base support 28 by screws T10-and tothe mounting block 264 by screws 222. -The chuck 258is xed on a rotatable shaft 214 which extends rearwardly through the slide 260 and through a vertically'elongated slot (not shown) in the block 264. The rearwardly projecting end of 'shaft 274 carries a` handle 216 that canV be rocked back and forth to movethe point v256 across the periphery of the grinding wheel here designated Vgenerally by the numeral 218.

In operation, the fixture is set up with the dressing points 288 and 266 disposed substantially as shown in Fig. 4 with respect to the grinding wheel 218. When thus` positioned, the point-,.208 is positioned vto dress the involute surface on one side of the wheel 228 and the point 256 is positioned to dress the periphery thereof.

To dress the periphery of the wheel it is merely necessary to. rock the holder or chuck 258 aboutthe axis of shaft '274 by means of handle 276. `As the chuck is rocked in this manner, the wheel dressing point 256 is caused to travel back and forth across the periphery of the wheel andA to dress-the same.

In order to dress the involute surface ofthe wheel withr the dressing point 200 in the position sho-wn .in the drawings, however, it is necessary to .disengage control arm 2|0 from the 7 c parallelogram linkage by removing screw 238. Thereafter, as the handle 86 is actuated to move the follower 84 along the left-hand cam surface 38, the parallelogram linkage acts through the.

crossbar H to move the point 200 along the involute surface of the wheel. 0f particular sig.

against cam surface 38 and thus prevents any A inaccuracies resulting from improper engagement of the follower with the cam surface.

Conversely, to dress the opposite involute surface of the wheel 218, it is merely necessary to reverse the dressing point 230 in the manner hereinabove described, move the spring arm 94 from the full-line to the dotted-line position, release control arm 2I2 from the parallelogram linkage, again engage control arm 2H) to the linkage by reinserting fastening screw 238, and actuate handle 85 to move follower 84 along the right-hand cam surface 4D. As the follower moves along the cam surface the parallelogram linkage is actuated in the manner hereinabove described to move the point 260 across the .meri--Y tloned involute surface of the wheel, and during such travel of the dressing point the control arm 2H) acts continuously to maintain the point exactly perpendicular to the surface being dressed. Also, it will be observed that during such operation, the spring |00 maintains the follower 18 pressed against the cam surface 40 to assure a true involute surface on the wheel.

Having thus described the invention, We claim: l. A grinding-wheel dresser comprising a support; a master cam carried by said support; pivoted links forming a parallelogram having opposed pivots, one pivot being fastened to the support and the other pivot having an extension constituting a follower for said cam member; a cross link pivotally connected to and longitudinally adjustable along opposite links forming said parallelogram; a wheel-dressing device having a wheel-dressing point, a chuck carrying said point, and a mounting supporting said chuck for oscil. lation on said cross link; a control arm extending between the chuck and one of the links forming said parallelogram; pivots connecting opposite ends of said control arm to said chuck and said one link respectively, and means holding said control arm against independent longitudinal movement relative to said pivots, said control arm being operative to hold the dressing point continually normal to the surface being dressed as the follower is moved along the cam surface.

2. A grinding-wheel dresser comprising a support; a pair of master cam members carried by said support and having spaced confronting cam surfaces; pivoted links forming a parallelogram having opposed pivots, one fastened to the support and the other having an extension consti.

tuting a follower for said cam members; a cross link pivotally connected to and longitudinally adjustable along opposite links forming said parallelogram; a wheel-dressing device having a wheel-dressing point and a chuck carrying said point, the chuck being mounted for rotation on and longitudinallyA adjustable along said cross link; control arms extending in opposite directions from said chuck and to the outer ends of adjacent links forming said parallelogram, pivots connecting the inner ends of said control arms to said chuck, pivots connecting the outer ends of the control arms to said adjacent links and means holding said control arms against independent longitudinal movement relative to said pivots, said arms being selectively disengageable from said links and operative to hold the dressing point continuously normal to the surface being dressed as the follower is moved along said cam surfaces.

3. A grinding-wheel dresser comprising a support; a pair of master cam members carried by said support and having juxtaposed cam surfaces; pivoted links forming a parallelogram having opposed pivots, one fastened to the support and the other having an extension constituting a follower for said cam members; a cross link pivotally connected to and longitudinally adjustable along opposite links forming said parallelogram; a wheel dressing device having a wheel dressing point and a chuck carrying said point, the latter being mounted for rotation on and longitudinally adjustable along said cross link; means detachably locking said-chuck in each of two positions 4 apart; and control arms pivoted to said chuck and to adjacent links forming said parallelogram, said arms being selectively disengageable from said links and operative to hold the dressing point continuously normal to the surface being dressed as the follower is moved along said cam surfaces.

4.r A grinding-wheel dresser comprising a support; a pair of master cam members carried by said support and having spaced confronting cam surfaces; pivoted links forming a parallelogram having opposed pivots, one pivot being fastened to the support and the other pivot having an extension constituting a follower for said cam member; a cross link pivotally connected to and longitudinally adjustable along opposite links forming said parallelogram; a wheel dressing device having a wheel dressing point and a chuck for said point, the chuck being mounted for oscillation on and longitudinally adjustable along said cross link; control arms at opposite sides of said chuck; means pivotally connecting the inner, adjacent ends of the arms to the chuck; and means pivotally connecting the outer, distal ends of the control arms to the parallelogram linkage, at least one end of each control arm being detachable to disengage the links from one of the members to which it is attached.

5. A grinding-wheel dresser comprising an upright support; a pair of master cams on said support having laterally spaced confronting cam surfaces; pivoted links forming a parallelogram having opposed pivots, one pivot being fastened to the support and the other pivot having a rearward extension disposed between said cam members and constituting a follower for said cam surfaces; a cross link pivotally connected to and longitudinally adjustable along opposite links forming saidv parallelogram; a wheel dressing device. including a mounting carried by and 1ongitudinally adjustable on said cross link, an oscil- -latable arm carried by said mounting and having an oiset terminal portion, a wheel dressing point on the offset portion of said arm, and means holding the arm in selected rotatably adjusted position; control arms at opposite sides of said oscillatable arms; means pivotally connecting the outer ends of said control arms to said parallelogram; and detachable means providing pivots for the inner ends of said control arms and connecting the latter to said oscillatable arm.

6. A grinding-wheel dresser comprising a support; a pair of master cams on said support having laterally spaced confronting cam surfaces; pivoted links forming a parallelogram having opposed pivots, one of said pivots being fastened to the support and the other of said pivots having a rearward extension disposed between said cam members and constituting a follower for said cam surfaces; a cross link pivotally connected to and longitudinally adjustable along opposite links forming said parallelogram; a wheel-dressing device including a mounting carried by and longitudinally adjustable on said cross link, an oscillatable arm carried by said mounting and having an offset terminal portion, a wheel dressing point on the offset portion of said arm, an adjusting block loosely mounted on said arm, and means detachably fastening the oscillatable arm to said adjusting block; and control arms pivoted to opposite sides of the adjusting block at one side of said oscillatable arm and at opposite sides of said parallelogram.

7. A grinding-wheel dresser comprising a support; a pair of vertically disposed master cams on said support having laterally spaced confronting cam surfaces; pivoted links forming a parallelogram having opposed pivots, one of said pivots being fastened to the support and the other of said pivots having a rearward extension disposed between said cam members and constituting a follower for said cam surfaces; a cross link pivotally connected to and longitudinally adjustable along opposite links forming said lparallelogram; a wheel-dressing device including a mounting carried by and longitudinally adjustable on said cross link, an oscillatable arm carried by said mounting and having an olset terminal portion, a Wheel dressing point on the offset portion of said arm, an adjusting block loosely mounted on said arm, sockets spaced circumferentially around said arm, and a detent carried by the block movable into said sockets to hold the arm in selected rotatably adjusted position in the block; and control arms pivoted to the adjusting block at opposite sides thereof and to opposite sides of the parallelogram linkage.

8. A grinding-wheel dresser comprising a support; a pair of master cams on said support having laterally spaced confronting cam surfaces; pivoted links forming a parallelogram having opposed pivots, one of said pivots being fastened to the support and the other of said pivots having a rearward extension disposed between said cam members and constituting a follower for said cam surfaces; a cross link pivotally connected to and longitudinally adjustable along opposite links forming said parallelogram; a wheel-dressing device including a mounting carried by and longitudinally adjustable on said cross link, ,an oscillatable arm carried by said mounting and having an offset terminal portion, a wheel-dressing point on the olset portion of said arm, an adjusting block loosely mounted on said arm, said adjusting block comprising hinged sections arranged in embracing relation to the arm and detachably fastened together on the arm, sockets at diametrically opposite sides of the arm, and a detent carried by the block movable into said sockets to hold the arm in selected rotatably adjusted positions in the block; and control arms at opposite sides of the Wheel-dressing device, said control arms being pivoted to the adjusting block at opposite sides thereof and to opposite sides of said parallelogram linkage, said control arms being selectively disengageable from said parallelogram linkage and operative to hold the dressing point continuously normal to the surface being dressed as the follower is moved along said cam surfaces.

HARRY H. GOTBERG. JOSEPH SILVAGI.

REFERENCES CITED UNITED STATES PATENTS Name Date Kopec June 15, 1943 Number 

